(A/N: I hope I'm not treading on anyone's toes by doing the change this way- I really like the concept of this but wanted to do all the transformation parts in one go! Feel free to do it differently if you want.)
Day 1
When you wake up, you notice your body feels a little smaller and your skin a little smoother. You've slimmed a little and your muscles are less thick. A couple of times during the day you feel a weird shiver and notice your body has slimmed more, and you swear your hands used to be larger. You have PE today, and at one point one of your classmates remarks they didn't realise you were that thin, but otherwise people don't really notice.
Day 2
In the mirror that morning you swear your face looks kinda different- your jawline is less pointed and your cheeks softer. Your T-shirts are weirdly loose on you, though your jeans are weirdly almost tighter because your hips have started to get wider and your butt is larger. Your shoes have started to feel too big too, so you buy some in a smaller size that are a much comfier fit. When you look at yourself in the bathroom mirror, you can see how much you've changed already- your figure looks way more girlish, and you feel way more comfortable with how you look.
Day 3
Most of the day passes normally, except for two big things. One is that when you're asked to read in one class, your voice cracks and sounds higher-pitched, and you feel embarrassed and have to carry on reading in a higher voice. The other is that at one point you feel a weird sensation in your chest, kinda sore but also intensely sensitive and nice. It's a sensation you've never felt anywhere else but... your cock. You can guess what's started to happen, so when you get home you rush to the bathroom and pull off your T-shirt. Your nipples are way larger and perkier! Your heart racing, you lock the door, strip off and start to take a shower. As soon as you start playing with your nipples you get an erection, and in your head you fantasize about having them played with and sucked on. When you start jacking off you orgasm surprisingly fast, and you feel way more cum pump from you than normal and wash down the shower drain. Weirded out and slightly tired by how intense that felt, you make sure to wear a vest under your T-shirt to reduce how stimulated your nipples get.
Day 4
You're woken up today by sleeping weird on your chest, and realise you've started to sprout. You aren't sure what size your boobs are, but thankfully the vest covers them nicely. By now the last few changes besides to your genitalia have come into force- your face looks much more like a girl's and your hair has started to naturally lengthen at an unnatural speed. Someone calls you 'pretty' as an insult, but you shrug it off figuring it's a good sign that you look that girlish. When you get home you pull off your T-shirt and vest, and exhale in relief as your boobs bounce free of the clothes. They seem to swell now they're unconstrained, and before you know it you have pert B-cups. Down below you realise your penis and testicles have started to shrink, and you feel aroused to see how your body's changing so much. You take another shower, and decide to not even touch yourself down there. Playing with your hard nipples and your soft breasts does the job- you get erect and cum just as hard as yesterday. You realise after you come down from the high that your body is working through semen and won't be producing any more- soon you'll have female parts down there. The thought makes you smile.
Day 5
The weekend! Now you can go shop for some stuff that'll affirm the girl you're becoming. You go around the clothes and second-hand shops in town and buy all kinds of cute clothes, from girls'-size shorts to cute tops to skirts to sundresses to, obviously, bras and other underwear. Satisfyingly, not only does no one think anything of you doing it, a few people even call you 'ma'am' and you don't hear a single 'sir'. When you get home, you try practically everything on. You put on your bra and feel like you never wanna take it off- having something to support your boobs feels so nice after two days of hiding them in a vest! You still have to wear boy's underwear instead of panties, but with how much your penis has continued to shrink, you can tell that won't be the case much longer. That evening, you jack off to porn on your computer for the first time in a while, and find that stuff focused on men is drawing your attention more. Even your sexuality has started to change, you realise, as you see men's handsome firm bodies and big hard cocks and realise that's what you feel attracted to now. When you cum, it feels normal at first, but then you feel a tensing sensation in your balls. They seem to push back up inside you, purged of cum and turning into their feminine counterpart. An aching, arousing emptiness surges in your castrated body, and you wish you could have it satisfied now, only able to cope because it'll only be another day or two.
Day 6
After several days of really intense changes, things are starting to wind down. You check from time to time hoping your penis will continue to shrink, and eventually you feel it start to, and race to the bathroom. You watch as it shrinks into a tiny sensitive nub, the skin around it fusing to your crotch as it forms a hooded nub. You have a clitoris now. Under it, your scrotum sinks into your crotch until you have an almost flat mound. Eager to feel your changed crotch, you rub the bud of your new clit and bite your lip to avoid yelling out with pleasure- it's more sensitive than your cock had ever been. You continue to massage it until you cum hard, but the empty sensation isn't fulfilled- you still need to be filled up.
Day 7
Around midnight, you're awoken by the transformation finally finishing off. You manage to get a mirror to between your legs, and see your mound peel open at its centre into a pair of lips- your vagina. Inside you your feminine parts all come together, and you have a womb and ovaries connected up to your new pussy hole.
A tingling sensation of arousal floods through you, and even if you wanted to you can't hold back the tide- you have to feel what a peak in this body is like! One hand reaches to one of your breasts and starts to tenderly cup it and rub and pinch at the nipple, while the other extends to your pussy, the thumb settling onto your clitoris while the fingers carefully tease your newformed slit.
The feeling is indescribable, just as intense as when you'd first jacked off in your boy's body, but instead of feeling like your body screaming at you 'I am male', it's like your body screaming at you 'I am female'. And as a result, it feels so much more right.
Your mind goes wild with fantasies, imagining people sucking at your breasts and pounding your pussy with their cocks, wanting to bring you to your peak and fill you with their cum.
You cum as a full girl for the first time in your life, and the satisfaction you feel is amazing. It's so intense you drift off to sleep within minutes.
The next day at school...